# Copyright 2018 Open Source Robotics Foundation, Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import sys

from example_interfaces.srv import AddTwoInts

import rclpy
from rclpy.callback_groups import ReentrantCallbackGroup
from rclpy.executors import ExternalShutdownException


def main(args=None):
    rclpy.init(args=args)

    try:
        node = rclpy.create_node('minimal_client')

        executor = rclpy.executors.SingleThreadedExecutor()
        executor.add_node(node)

        # Node's default callback group is mutually exclusive. This would prevent the client
        # response from being processed until the timer callback finished, but the timer callback
        # in this example is waiting for the client response
        cb_group = ReentrantCallbackGroup()
        cli = node.create_client(AddTwoInts, 'add_two_ints', callback_group=cb_group)
        did_run = False
        did_get_result = False

        async def call_service():
            nonlocal cli, node, did_run, did_get_result
            did_run = True
            try:
                req = AddTwoInts.Request()
                req.a = 41
                req.b = 1
                future = cli.call_async(req)
                result = await future
                node.get_logger().info(
                    'Result of add_two_ints: for %d + %d = %d' %
                    (req.a, req.b, result.sum))
            finally:
                did_get_result = True

        while not cli.wait_for_service(timeout_sec=1.0):
            node.get_logger().info('service not available, waiting again...')

        timer = node.create_timer(0.5, call_service, callback_group=cb_group)

        while rclpy.ok() and not did_run:
            executor.spin_once()

        if did_run:
            # call timer callback only once
            timer.cancel()

        while rclpy.ok() and not did_get_result:
            executor.spin_once()
    except KeyboardInterrupt:
        pass
    except ExternalShutdownException:
        sys.exit(1)


if __name__ == '__main__':
    main()
